let a: number;
a = 10;
// a = 'abc'; // 报错

let b: string;
b = 'abc';

let c: boolean = true;

let d = true;

/**
 *
 * @param a {number}
 * @param b {number}
 * @returns {number}
 */
function sum(a: number, b: number) {
    return a + b;
}

/*function sum(a: number, b: number): number {
    return a + b;
}*/

console.log(sum(1, 2));